When a cigarette is smoked, visible smoke is produced, by mainstream smoke spillage, exhale smoke and as well sidestream smoke which is generated by the burning cigarette between puffs. Cigarette smoke is considered objectionable by some persons and has led to no-smoking laws of varying degrees of strictness in certain .jurisdictions and environments.
A number of prior proposals have been made with respect to structures which are designed to minimize or eliminate the formation of visible smoke, when a cigarette is smoked. However, no device disclosed in the art known to the applicants provides for not only the substantial elimination of all the visible smoke but also provides the same smoking taste and quality to the smoker as if smoked in the normal way.
Several devices of various degrees of sophistication have been developed to filter sidestream smoke and/or exhale smoke. U.S. Pat. No. 4,052,179 discloses an example of the standard type of ashtray system which draws sidestream smoke through a charcoal filter contained within a fine wire or glass fibre mesh. A deodorant pad may be included on the exhaust side of the system to mask any remaining cigarette smoke odours not removed by the charcoal filter.
Another form of sidestream smoke filter is disclosed in U.S. Pat. No. 4,685,477. A cigarette is inserted in the device which is tubular in shape and is open at each end. When the cigarette is inhaled fresh air is drawn in through an air intake. The lit cigarette is positioned inside the tubular filter. As the cigarette continues to bum, the sidestream smoke permeates the surrounding tubular shaped filter. Because the burning cigarette is housed within the filter, the filter material cannot be affected by heat and is not readily ignited by the cigarette ember. During smoking of the cigarette, the enclosed smoke contaminates the cigarette paper and cigarette tobacco resulting in unsatisfactory taste.
U.S. Pat. No. 4,200,114 discloses a smoker's mask which may be placed on the smoker's face. The system provides for inhale and exhale cigarette smoke where all sidestream and exhale smoke is filtered through a single filter. A complex arrangement of check valve is provided to ensure that all smoke passes through the filter or is contained within an enlarged smoking chamber.
U.S. Pat. No. 4,790,332 discloses a smoker's accessory in which the cigarette is totally housed. Both sidestream and exhaled smoke are filtered by the same filter. The filter usually consists of two layers. An inner filter made of hepa or like material removes particulates from cigarette smoke. The outer layer of the filter is a polyurethane foam or like material impregnated with charcoal for removing odour from the air as it passes from the inside of the device through the filters and into the surroundings.
U.S. Pat. No. 4,899,766 describes a smoke catcher which provides for capture of both the sidestream and exhaled smoke. A fan is used in conjunction with filters to draw the sidestream smoke and exhaled smoke through filters before discharge into the surroundings. The filters comprise in series two or more filter elements. The exhaust fan is located downstream of the filter elements. Alternatively, the exhaust fan may be located to exhaust the smoke to the outside without filtration.
U.S. Pat. No. 4,993,435 discloses a smoker's accessory which captures sidestream smoke for inhalation by the user and is provided with an exhale filter arrangement. Several serially arranged filter disks are provided. The filter disk may include charcoal and the like or pressed paper material having a suitable porosity for purposes of filtering the exhaled smoke.
A filter disk has also been used in a smoker's accessory having a powered fan within the hand-held unit. The sidestream smoke is drawn from the lit cigarette through a filter disk before discharge to the surroundings in the manner shown in U.S. Pat. No. 4,637,407.
Considerable efforts have been made in the area of filters as provided on cigarettes to effect a partial filtration to reduce the amount of tar and nicotine inhaled by the smoker. It is appreciated that cigarette filters however are not designed to remove substantially all of the cigarette smoke so that the smoker continues to experience the usual taste and flavour. Cigarette filters for example, which are tubular in nature are designed to filter some of the smoke particles from the smoke stream. U.S. Pat. No. 3,685,523 discloses a tubular type of cigarette tip filter which partially filters the cigarette smoke as it passes from the interior of the tubular filter to the exterior thereof before inhale by the smoker. A similar type of filter is described in U.S. Pat. No. 3,854,384 involving a tubular filter only offset with respect to the central axis of the cigarette. Both filters are designed to be inefficient to allow the various components of cigarette smoke to pass through the filter so that the smoker realizes the desired taste and flavour.
Canadian Patent 1,057,924 as issued to the applicant describes a method of producing polymeric fibres of micron size which can be used in cigarette filters. Such micro-fibre has been used in cigarette filters of the type described in applicant's U.S. Pat. No. 3,882,877 and international application WO90/09741. The micro-fibres produced by the method of Canadian Patent 1,057,924 have increased filtration efficiency compared to cigarette filters of the standard cellulose acetate, charcoal and the like. In order to take advantage of the efficiency of those filters a thin cylindrical filter is provided in the filter tip of a cigarette as described in WO90/09741 which provides for uniform tar delivery while smoking the cigarette.
None of the devices described in this prior art provides however, in a portable and compact structure, the significant features of substantial elimination of both sidestream and exhale smoke and that the smoker experiences the same degree of smoking taste and quality as when smoking a cigarette normally.
In accordance with this invention, a filter is provided which may be adapted for use in filtering cigarette smoke. The filters are intended to be used with devices such as a compact portable smoker's accessory which permits a smoker to smoke a cigarette while at the same time substantially eliminating at least the sidestream smoke and exhaled smoke. Such device may include an enclosure in which the cigarette is located for smoking. The smoker may draw on the cigarette located within the enclosure to smoke the cigarette and also exhales back into the device where the appropriate filters process either the sidestream smoke or the exhaled smoke.
A fan may be provided in the enclosure to ensure a powered air flow through the enclosure so as to supply fresh air as required for proper burning of the cigarette and also to decrease the temperature of air surrounding the cigarette, so as to prevent scorching of cigarette paper and prevent drawing of the hot air from the enclosure by the smoker which would result in unsatisfactory taste and flavour to the smoker. In this way, the same degree of smoking taste and quality could be maintained as if the cigarette were smoked normally.
Low pressure drop highly-efficient filtration material generally is employed for filtering both sidestream smoke and exhale smoke. Such highly-efficient filtration material generally comprises a mass of micro-fine fibres. Such filtration conveniently is effected in separate compartments or the same compartments within the enclosure, by different filter elements.
The filter element or elements may be constructed to permit filtration of cigarette smoke to be effected prior to contact of such smoke with the permanent structural elements of the smoking apparatus, so as to minimize contamination of non-disposable elements of the device by tobacco smoke components.
The smoking apparatus is constructed so that at least the tobacco portion of the cigarette is enclosed within the unit during smoking to ensure that all sidestream smoke is filmed by the unit, and also provides for filtration of exhale smoke such that the activity of smoking is not readily apparent to the casual observer. The smoking apparatus may also be constructed or used without providing for the exhale smoke filtration.